Preprints  

We describe the design and performance of a new noble gas mass laboratory dedicated for the development and application to cosmogenic nuclides at the University of Cologne (Germany). At the core of the laboratory are a state-of-the-art high mass resolution multicollector Helix MCPlus (Thermo-Fisher) noble gas mass spectrometer and a novel custom-designed automated extraction line; including a laser-powered extraction furnace. Performance was tested with intercomparison (CREU-1) material.

When using trapped-charge dating methods to determine the time of deposition of a sediment, it is of great importance to know whether the signal containing the age information, has been completely erased before burial or if a residual signal is inherited. We examined the residual doses of the quartz ESR signals of young fluvial sediments from the lower Rhine terraces with known luminescence ages. We found varying but large residuals indicating an incomplete bleaching of the quartz ESR signals.

We use X-ray scanning to improve the quality of geologic ages derived from measuring the products of cosmic rays in the mineral magnetite. We show that the presence of other minerals can lead to wrong age estimates. By detecting those minerals with X-rays and analyzing only pure magnetite, this problem can be avoided. We also measure the rate at which helium from cosmic rays is produced in magnetite, which can be used for similar studies in the future.

Fission tracks are generated in minerals due to spontaneous fission of U-238. The initial track length decreases with time due to recrystallization. The age of a track can be calculated by counting the number per volume of the shorter tracks and include the decay constant. However, the theoretical order of track length versus time is disrupted by uncertainties. We have shown how the order can be reestablished. It is then possible to determine the age of tectonic events such as uplift or burial.

Cooling ages date the time at which minerals cross a certain isotherm on the way up to Earth's surface. Such ages can be measured from bedrock material as well as from river sand. If spatial variations of bedrock ages are known in a river catchment, the spatial distribution of erosion can be inferred from the distribution of the ages measured from the river sand grains. Here we develop a new tool to help such analyses, with particular emphasis on quantifying uncertainties due to sample size.

We apply new rock luminescence techniques to a well-constrained scenario of the Beinn Alligin rock avalanche, NW Scotland. We measure accurate erosion rates consistent with independently-derived rates and reveal a transient state of erosion over the last ~4,000 years in the wet, temperate climate of NW Scotland. This study shows that the new luminescence erosion-meter has huge potential for inferring erosion rates on sub-millennial scales, which is currently impossible with existing techniques.

A conventional isochron is a straight line fit to two sets of isotopic ratios, D / d and P / d, where P is the radioactive parent, D is the radiogenic daughter and d is a second isotope of the daughter element. The slope of this line is proportional to the age of the system. An inverse isochron is linear fit through d / D and P / D. The horizontal intercept of this line is inversely proportional to the age. The latter approach is preferred when d < D, which is the case in Re–Os and K–Ca geochronology.

Our contribution enhances the infrared-radiofluorescence dating technique, used to determine the last sunlight exposure of potassium feldspars in a range of about 600 to 600.000 years backwards. We recorded radiofluorescence images of fine sands and processed them with tailored open-source software to obtain ages from single grains. Finally, we tested our new method successfully on two natural sediment samples. Studies in Earth science will benefit from improved age accuracy and new insights.

A novel technique for the uranium-lead dating of geologically young carbonates is described and tested. The technique expands our ability to date geological events such as fault movements and past climate records.

The timing and duration of fluid activity within a gold deposit enables a greater understanding of how the deposit evolved and thus help future mineral exploration. This research uses high resolution dating methods to unravel the overprinting fluid activity at the Martabe gold field in Sumatra. Methods outline in this report can be applied to deposits globally.

Luminescence dating requires irradiating the sample in the laboratory. Some concerns have been published recently about the reliability of the calibration procedure. Here we have addressed these concerns. We found that the interplay between geometrical parameters such as grain size and aliquot size impact on the calibration more than previously thought. The results allow us recommending improved calibration procedure to enhance the reliability of the calibration value.

We generated a synthetic dataset applying published kinetic models and distinct annealing kinetics for the apatite fission-track and (U-Th)/He methods using a predetermined thermal history. We then tested how well the true thermal history could be recovered under different data interpretation schemes and geologic constraint assumptions using the Bayesian QTQt software. Our results demonstrate that multikinetic data increase time-temperature resolution and can constrain complex thermal histories.

Here we present the foundation dataset for “TephraNZ”, a formal, comprehensive, open access, reference dataset of glass-shard compositions for New Zealand tephras. We geochemically characterise 45 eruptive episodes ranging from Kaharoa (c. 636 cal. yrs BP) to the Hikuroa Pumice member (c. 2.0 Ma) from six or more caldera sources, most from the central Taupō Volcanic Zone.

Artificial intelligence techniques are capable of detecting fission tracks automatically in minerals. The here presented AI-Track-tive software can be used to automatically determine fission track densities for apatite fission track dating studies. Apatite fission track dating is mainly applied to tectonic studies studying exhumation rates in orogens. Now, time-consuming manual track counting is replaced by deep neural networks capable of automatically finding the large majority of the tracks.

We introduce a new model of confined fission-track revelation, which simulates the etching process and accounts for variable along-track etching rates. This complete characterization explains many observations, including community difficulty in obtaining consistent track length measurements. It also provides a quantitative basis for optimizing etching procedures, and ultimately deriving more robust and reproducible fission-track ages and thermal histories.

Potassium-based geochronology, including the ⁴⁰Ar/³⁹Ar and K-Ar methods, provides critical constraints on the timing and duration of many events and processes in earth history. These methods assume that a key parameter, the fraction of potassium with a mass of 40, does not vary in some relevant materials. Some recent work has identified some variability in these materials. This work examines the effects of this variability on calculated K-Ar and ⁴⁰Ar/³⁹Ar ages.